Trautmann's triangle anatomy with application to posterior transpetrosal and other related skull base procedures

Trautmann's triangle (TT) faces the cerebellopontine angle and is exposed during posterior transpetrosal approaches. However, reports on the morphometric analysis of this structure are lacking in the literature. The goal was to better understand this important operative corridor. TT was exposed from an external approach (transmastoid) in ten cadavers (20 sides) and from an internal approach on 20 dry adult temporal bones. Measurements included calculation of the area of TT and the distance of the endolymphatic sac from the anterior border of the sigmoid sinus. The area range of TT was 45-210 mm(2) (mean 151 mm(2); SD 37 mm(2)). Three types of triangles were identified based on area. Type I triangles had areas less than 75 mm(2), Type II areas were 75-149 mm(2), and Type III areas were 150 mm(2) and greater. These types were observed in 37.5%, 35%, and 27.5% of sides, respectively. The distance from the jugular bulb's anterior border to the posterior border of the posterior semicircular canal ranged from 6 to 11 mm (mean 8.5 mm). The endolymphatic sac was located in the inferior portion of TT and traveled anterior to the sigmoid sinus. The horizontal distance from the anterior edge of the sigmoid sinus to the posterior edge of the endolymphatic sac ranged from 0 to 13.5 mm (mean 9 mm). Additional anatomic knowledge regarding TT may improve neurosurgical procedures in this region by avoiding intrusion into the endolymphatic sac and sigmoid sinus.